In the intensive raising of pigs, the sow at the time of birthing is moved to a farrowing pen which includes a farrowing crate which defines a central area in which the sow can lie and a two side creep areas in which the piglets can lie, move about and can move to the sow for accessing the nipples.
The farrowing crate generally includes a metal framed structure which confines the sow so as to prevent the sow from lying in the side areas and thus crushing the piglets. The crate and flooring system allows the sow to stand so that the sow can feed from a feeder located at a front of the crate on an outlet door. The crate is generally bolted to the flooring system or to the surrounding concrete structure so that it stands up from the floor and extends from the front to the rear of the pen.
Underneath the pen is provided a manure containment pit and over the pit is mounted a flooring structure on which the sow can lie and stand and on which the piglets can lie and move.
The farrowing pens are generally arranged side by side in a row with the front gate opening on to an alley way.
In recent years, the importance of a high level of sanitation in the production of pigs has been appreciated to avoid transfer of diseases from one litter to the next. The purpose of the pit and the supporting flooring system above the pit on which the animals stand is in order to provide improvements in hygiene so that the manure from the animals falls through the floor into the pit and is separated from the animals standing on the floor. The floor can then be cleaned to prevent bacteria, viruses and funguses from being harbored in the flooring and pen system.
This type of system using a pit was implemented in approximately the 1950s. The first type of flooring used for the purposes of extending across the pit and supporting the animals was in many cases a simple wooden flooring formed from a series of parallel slats. At around the same time, aluminum flooring was also used in the form of extruded elongate T-bars. The vertical web of the T-bar provided sufficient strength to enable this structure to span the length of the farrowing crate which is generally of the order of 7 feet. The T-bars had a horizontal upper surface and were mounted side-by-side so that the bars were arranged in spaced position with a slot or opening between the two adjacent T-bars allowing the manure to fall through for collection in the pit.
The aluminum T-bars had two disadvantages. Firstly, any electrical conduction between the aluminum T-bars and another conductive material generated a highly aggressive corrosion caused by galvanic action. In this corrosion, two dissimilar materials, such as the steel of the farrowing crate and the aluminum of the flooring, in conjunction with an electrolyte provided by the liquid manure provides a galvanic action rapidly corroding the aluminum T-bars. Galvanic corrosion is particularly pernicious in that it is generally invisible but degrades the material until it becomes brittle and fails, generally catastrophically, dumping the animals into the pit.
Secondly, the upper horizontal surface of the aluminum since it was extruded was linear and flat and thus was slippery so that the animals tended to have difficulty standing. Sows particularly are not agile and accordingly have difficulty rising from lying position. Any slipping of the feet can cause the sow to fall or to splay which can injure the sow and can crush many piglets. It is well known that the crushing of piglets is a significant problem and can dramatically reduce the efficiencies of pig production if significant numbers of the piglets are crushed.
Some attempts were made to overcome these problems. In regard to the galvanic corrosion, the T-bar slats were electrically insulated from the underlying concrete structures by providing an insulating plastic strip lying on top of the concrete and underneath the T-bar slat. However this attempt was generally unsuccessful because any electrical connection including through the steel crate, drinking devices or electrical devices over the life of the product, which is expected to be several years, caused such galvanic corrosion. Such electrical connection is difficult to avoid in the presence of the electrically conductive manure which can bridge insulators. Some attempts were made to reduce the slipperiness of the horizontal upper surface by attaching abrasive and welded strips.
Neither of these attempts were of considerable success and eventually the aluminum T-bar slats were abandoned and no such flooring is currently manufactured today and is likely that all such flooring previously installed has become corroded and replaced.
In a published article in the paper "Feld und Wald" No. 16 of 16th Apr. 1976 is disclosed the use of elongate aluminum panels which span the space across the pit and are therefore supported at respective ends on the sides of the pit. This disclosure is similar to the aluminum T bars and is around the same time as the use of the T-Bar system. This does not mention corrosion and does not seem to have lead to wide scale adoption of this technique.
In general, therefore, the use of aluminum for flooring has been abandoned in view of the above problems and it is believed that those skilled in the art would reject use of aluminum or similar materials in view of these problems.
A subsequent approach for providing suitable flooring involved the provision of supporting beams across the pit and the laying over the supporting beams of a material known as "Tenderfoot" which comprises an expanded metal coated in a plastics material. The expanded metal is steel and the plastics material reduces corrosion of the steel and provides a more suitable flooring for the piglets.
A yet further proposal shown for example in the brochure "Polygrate" of the present assignee comprises a wholly plastics system in which the beams are extruded from fiberglass reinforced resin and the flooring covering those beams is formed from injection molded plastics material.
Both the Tenderfoot flooring and the Polygrate flooring have achieved considerable success and are widely used.
One problem that has however arisen with these materials is that the flooring is less suitable for location under the sow since the floor is less able to resist the high level abrasion from the heavy feet of the sow.
Flooring of cast iron grate or panels has therefore been manufactured for use under the sow. An alternative type of metal flooring which can resist the abrasion is that of a welded parallel steel rod construction known as "Tribar".
However these floors are unsuitable for positioning under the piglets since the piglet should be kept warm and the cooling affect of the thermal conductivity of the metal and the chimney affect of the air from pit passing through the openings in the floor tends to cool the piglets at too high a rate. An attempt has been made to solve this problem by increasing the temperature of the farrowing crate and this of course causes stress to the sow who is used to a temperature much lower than that is required by the piglets.
The solution currently widely being used is therefore to provide a plastics flooring or a plastics coated flooring In the area under the piglets and to provide under the sow a flooring of a cast iron grate. The cast iron grate can be laid on supporting beams or in some cases is supported on metal webs located at the edge of the plastics flooring. One example of arrangement of this type is shown PCT International Application WO95/18525.
However cast iron has significant disadvantages. Cast iron is difficult to maintain hygienic because it is porous and hence retains moisture carrying bacteria in the pores and has a surface which has a tendency to retain moisture and to remain wet again allowing bacteria to remain and multiply on the surface. Yet further, the cast iron tends to corrode by developing rust on the surface. While this corrosion is generally insufficient to cause structural break down, it does provide further pores and spaces for harbouring moisture and therefore dangerous bacteria. Despite these disadvantages, the cast iron grate or slat under the sow represents the current standard in the art.
Another arrangement is disclosed in DE G9320652 assigned to Ikadan Systems of Denmark published in 1995 which corresponds to U.S. Pat. No. 5,687,534 issued 18th Nov. 1997. This discloses a steel beam system with the beams extending across the manure pit to support the flooring. The flooring includes cast iron gratings which are arranged to be supported by the beams. In order to support the cast iron gratings in a manner which is more suitable, the applicant provides a plurality of hanger members which are formed of plastics material. These hangers are provided for structural reasons and are not in any way concerned with electrical insulation.
Yet another arrangement uses PVC pipes for supporting the sow and attempts to cool the sow by communicating heat from water in the pipes to the drinking water. This arrangement was commercially unacceptable as the flooring could not accommodate the hard wearing effect of the feet of the animal. This arrangement is shown in a brochure by INSERT.